Susceptibility of convalescent turkeys to pulmonary aspergillosis.

Pulmonary lesions resulting from Aspergillus fumigatus inoculation were assessed in convalescent turkeys and compared with those in previously noninoculated (control) turkeys. In addition, lesions observed in small Beltsville white (SBW) turkeys were compared with those in broad-breasted white (BBW) turkeys challenged with the same inoculum. Turkeys were challenged by unilateral posterior thoracic air sac (PTAS) inoculation, rechallenged via the contralateral air sac after 5 wk, and then necropsied 1 wk later. Pulmonary lesions induced by the initial challenge had resolved in 6 of 10 SBW and 9 of 10 BBW turkeys. However, convalescence did not protect against pulmonary aspergillosis subsequent to rechallenge; 10 of 10 SBW and 9 of 10 BBW developed granulomatous pulmonary lesions on the side of reexposure. A greater proportion of control SBW turkeys developed pneumonia and airsacculitis following challenge as compared with the BBW breed. Lesions were limited to the lower respiratory tract in all turkeys and were confined to the ipsilateral lung and PTAS in the singly inoculated control turkeys. This study demonstrates that convalescence from pulmonary aspergillosis does not confer protection against rechallenge but may, instead, decrease resistance to subsequent infection.